I would guess that the "hottest day" syndrome is back with us again today and this will be parleyed into one swallow does make for AGW. Indeed, i am surprised that the "hottest day" did not obviously trigger a rash of AGW stories in the media - or maybe I have stopped seeing them.
I haven't really seen anything in the UK media which attempts to link it to AGW so far. I get the impression that nowadays the media limits itself to associating flooding with AGW and tends to steer clear of temperatures, possibly as a result of the 'snow is a thing of the past' debacle.
I vaguely remembered that the last time, back in 2006, that this 'hottest July day ever' story came up, a sceptical journalist called Ross Clark writing in the Times pointed out that there had been a higher UK temperature in July recorded in Victorian times. The Times is now of course unreferenceable as it has gone behind a pay wall, but I managed to find some blog called "The Daily Duck" where the blogger happened to write a post based on the Clark article and seems to have included most, if not all, of the text of the article:
From the blog post it looks like the Victorian record temperature was 38.1 deg C or 100.6 deg F on 22nd July 1868 at Tonbridge in Kent. This record, which was listed in 1950s textbooks, was apparently thrown out because the thermometer and housing were not considered acceptable by modern standards.